A 2-year cross sectional investigation is proposed to study the relationship between maternal transmission of Strep. mutans and primary infection of infants by the organism. The subject population will consist of healthy infants that harbor 6 to 8 primary incisor teeth, and their mothers. The infant subjects will all be patients of the Out Patient Clinic of The Children's Hospital of Philadelphia. Approximately 300 mother-infant pairs will be evaluated. Saliva samples will be obtained from the mothers and pooled plaque specimens will be simultaneously collected from their infants. The number of C.F.U.'s of Strep. mutans per ml of saliva will be determined for each maternal saliva specimen. In addition, the infant's plaque sample will be evaluated for the presence or absence of the organism. The resulting data will be utilized in a statistical model that permits testing of the following hypotheses: 1) The mean salivary level of Strep. mutans in a population of mothers whose infants harbor the organism is statistically different than the mean salivary level of Strep. mutans in a population of mothers whose infants do not harbor the organism. 2) There is a statistically significant increase in the frequency of isolation of Strep. mutans from a population of infants whose mothers harbor salivary levels of the organism in excess of 10 to the 5th power cells per ml saliva as compared to the frequency of isolation from infants whose mothers harbor less than 10 to the 5th power cells of the organism per ml saliva.